Refrigerating apparatus



Oct. 5, 1937. G c PEARCE 2,094,811

v REFRIGERATING APPARATUS I I H Fil p 2 1954 2 Sheets-Sheet 1 ATTO Oct. 5, 1937. exc. PEARCE 2,

' I REFRIGERATING APPARATUS Filed Sept. 29, 1934 2 Sheets-Sheet 2 WENTOR. M, v 1% 4 ATTOI; 15v;

Patented Oct. 5, 1937 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS Application September 29, 1934, Serial No. 746,245

13 Claims.

This invention relates to refrigerating apparatus particularly of the type including a compressor, a condenser and an expander and more particularly to an improved-means for unloading the compressor at the time of starting after an idle period.

In refrigerating apparatus of the character described, particularly those in which a hermetically sealed motor-compressor unit is used, difli culty is sometimes encountered in getting the motor-compressor unit to start after an idle period, due to the fact that the starting torque of the electric motor is necessarily low due to the limitations inherent in a sealed unit construction and is insufficient to start the compressor. under full load. Various unloading de-.

vices have been in use heretofore, all of which employ some mechanism within the compressor unit itself usually for operating a valve to relieve the load on the compressor during the starting period or until'the motor has come up to speed. It has been diflicult to construct unloading devices of that type without the use of numerous small parts which are apt to get out of order, and being within the sealed casing of the unit, are thus extremely inaccessible for repair.

It is an object of the present invention, therefore, to devise a novel means and method for unloading a compressor which may be utilized in connection with a hermetically sealed motorcompressor unit and which avoids the use of any additional mechanism within the sealed casing of such a unit.

A further object is to provide an automatic mechanism which will operate to cause reverse rotation of the motor-compressor unit before forward rotation is initiated at each time that the main circuit to the motor is closed. I

It is also an object to provide a novel switch for a motor-compressor unit which will initiate reverse rotation of the motor before initiatin the forward rotation.

It is a further object to provide a novel control switch for a motor-compressor unit which controls not only the direction of rotation of the motor in proper sequence to secure the unloading of the compressor, but also controls the starting windings of the motor to disconnect.

them after the motor has come up to speed.

A further object is to provide a switch for controlling the direction of rotation of a motorcompressor unit and for controlling the starting windings in such a manner that it is impossible for the motor to be placed into normal running condition in the reverse direction.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

This application is related to application Serial No. 745,956, filed September 28, 1934, in which Edward B. Newill is the applicant and in which means whereby the motor positively operates the compressor first in one direction to unload the compressor and means whereby the motor will thereafter positively operate the compressor in the opposite direction to compress fluid is claimed.

In the drawings:

Fig. 1 is a vertical cross section of a-motorcompressor unit showing diagrammatically the elements of a refrigerating system;

Fig. 2 is a cross section on line 22 of Fig. 1; and

. Fig. 3 is a perspective view of a switch for controlling the motor of Fig. 1 and showing diagrammatically the circuit connections between the switch and the motor.

Referring now to Fig. 1, there is shown a refrigerating system comprising a hermetically sealed motor-compressor unit In having an outlet l2, from which compressed refrigerant is delivered by means of a conduit I4 to a condenser l6. Refrigerant condensed in the condenser i6 is collected in a receiver l8, whence it is delivered by a conduit 20 to an expansion device, preferably a fixed restrictor 2|. The restrictor 2| permits the refrigerant to expand into an evaporator 22 for withdrawing heat from an object to be cooled (not shown). The expanded refrigerant is delivered by means of a conduit 24 to the in.- let 26 of the motor-compressor unit ID. A suitable automatic control switch 28 may be provided for maintaining substantially constant temperatures, the switch illustrated being of the type comprising a thermostat responsive to evaporator temperatures.

The motor-compressor unit may be of any well known type having a prime mover which may be operated in either direction of rotation and having a compressor of the type in which the direction of fluid flow therethrough is reversed on reverse rotation thereof. In the form illustrated in the drawings, the unit comprises a hermetically sealed housing 30 having a central stationary hollow shaft 32 on which is journalled the drive shaft 34 for the motor-compressor unit. The shaft 34 carries at its upper end the rotor 36 of an electric motor. A statorassembly 38 is secured to the inner wall of the housing 38 in a suitable manner and may be of any suitable type capable of operating the rotor 36 in either direction. For example, for use with single phase alternating current, the motor may be either of the split phase or capacitator type having the lead-in connections to the running winding separate from and independent of the lead-in connections to the starting winding rather than having a common lead-in to one side of each. At the lower end of the shaft 34, there is formed an eccentric 48 on which is journalled a cylindrical impeller member 42. A compressor body member 44 is secured to the bottom portion of the housing and includes a cylindrical compression chamber within which the impeller 42 is given a revolving motion by the eccentric 48. A spring pressed divider block 46 (see Fig. 2) divides the compression chamber into a suction space and a compression space. The inlet connection 26 is located in the base plate of the compressor body adjacent one side of the divider block 46, while an exhaust orifice 48 having a flapper valve 58 is provided in the top plate of the compressor body adjacent the opposite side vof the divider block 46. The exhaust orifice 48 and flapper valve 58 are shown .in dotted lines in Fig. 2 although it will be understood that they are located above the plane upon which the section of Fig. 2 is taken. The gas discharged from the orifice 48 is freed of lubricant by an enclosure member 52 surrounding the compressor body and passes outwardly and upwardly through the air gap of the motor to enter the hollow shaft 32 through one or more openings 54 at the top thereof, whence it is conducted through the hollow shaft 32 to the outlet connection I2. Each of the four lead-in connections to the motor are carried throughthe housing by suitable insulated terminal bushings 56, only one of which is shown, and each of the terminals is connected to a control switch 58 located between the motor and the thermostatic switch 28..

Referring now to Fig. 3, the control switch 58 preferably comprises a snap acting reversing switch 68 having a pair of movable contacts 62 having active contact faces at both the top and bottom of each. The. reversing switch 68 may be actuated by a bimetallic member 84 which is adapted to act as a timer in accordance with the rate of current flow therethrough. Each of the movable contacts 62 is adapted to engage alternately either a pair of bottom contacts 66 or a pair of top contacts 68. A master switch for the starting winding is also provided in the switch 58 and comprises a relay including an electromagnet I8 having a movable armature I2 adapted to actuate a movable master contact I4 which coacts with a fixed master contact I6. Suitable stop means is provided for the armature I2 comprising a resilient bumper I8 located on a pin 88 passing through a hole in the armature I2 and anchored to the base member 82. The switch 58 also includes a timer switch for controlling the relay coil I8 and which preferably comprises a bimetallic actuating member 84 having a movable contact 86 coacting with a fixed contact 88 for shunting the relay coil I8.

The circuit connections from the line through the switch 28 and switch 58 to the motor are made as follows: one side 98 of the line is connected by a conductor 92 to a terminal 84 of the running Winding 96. The side 98 is also connected by a conductor 98 to the master contact I4. The fixed master contact I6 is connected by tors II contact 66 of reversing switch 68.

electro-magnet I8. The electro-magnet I8 is in I turn connected to the other terminal H8 of the runningwinding 96 by conductor H2 and to the fixe end of the bimetal timer 84 by conducand H4. The fixed end of timer 84 is connected by conductor H5 to the other bottom The movable end of the bimetal'timer 84 is connected by.conductor H6 to the other top contact 68 of reversing switch 68. The terminals H8 and I28 of the starting winding I22 are connected to the movable contacts 62 of the reversing switch 88 by the conductors I24 and I26.

In operation assuming that the motor-compressor unit has been idle for a suflicient interval to permit pressure to build up in the compression-chamber by gas leakage, but that insuflicient time has elapsed for the pressure within the evaporator to become equal to the pressure within the condenser by the passage of refrigerant through the restrictor 28, it will be noted that any leakage of high pressure gas from within the housing 38 into the suction side of thecompression chamber will immediately pass through the inlet connection 26 through conduit 24 into the evaporator 22. In other words, the suction side of the compression chamber is always at evaporator pressure regardless of leakage within the compressor while the compression side gradually builds up to condenser pressure.

If it were attempted to start the motor-compressor unit forwardly under these conditions, it will be seen that the compressor is under full load at the instant of starting and unless the motor be made much larger and more powerful than is necessary for normalrunning, its starting torque will not be sufiicientto overcome force of the compressor.

With the present invention, however, the starting coilsof the electric motor are placed in circuit with the line and with the running coils in such a manner that the first rotation of the motori the resisting compressor unit is in a backward direction. This in effect causes the compressor to pump refrigerant from the compression chamber and from the exhaust orifice 48 as far up as the seat of the valve 58 into the inlet connection 26 and suction pipe 24. A single revolution of the motor-compressor unit backwardly will serve to completely exhaust the compression chamber and exhaust orifice 48 with the result that the pressure in the compression chamber is made at least as low as the pressure in the suction conduit 24 and often lower. If the reverse rotation be continued, the efiect will be substantially negligible and serve merely to maintain the low pressure condition within the compression chamber.

If now the connections to the starting winding be reversed relative to the running winding, the motor will be caused to rotate forwardly and will be able to start eifectively since the compressor will have at least a zero starting resistance. If the pressure in the compression chamber has been reduced to a point below that in the suction conduit 24, there will be a slight assistance from the compressor in starting the motor forwardly. As soon as the motor comes to speed, the starting in series with the starting winding I22.

to the starting winding I22.

winding may be disconnected from the line and the motor caused to run normally on the running winding alone, as is well known in the art.

The switch 58 operates to cause the sequence of operations described above automatically at each time that the line circuit is closed after an interruption in current supply to the motor. When the bimetal actuator 84 is cold after a period of idleness, it maintains the switch 60 in the down position closing the contacts 62 and 66. This prearranges the apparatus for connecting the starting winding I22 to the line in such relation to the running winding 86 that the motor will run backwardly. When the switch 28 is first closed after a period of idleness, the running winding 96 is placed in circuit across the line in series with the switch 28, the bimetal actuator 64 and the electro-magnet I0. The relay is calibrated so that it will close on initial surge of current to the running winding alone, but will not stay closed on the normal running current to the running winding alone. This energizes the armature I2 causing the master contacts I4 and I6 to close the circuit to the starting winding I22. The starting winding I22 is thus placed in circuit across the line in series with the switch 28, bi-

metal actuator 64, and relay coil I0 as well as the master contacts I4 and I6 and the reversing switch contacts 62 and 66. It will be noted that the entire current to the motor passes through the bimetal actuator 64 and through the relay coil III. This causes a rapid heating of the former, resulting in its flexing upwardly to actuate the reversing switch 60 opening the contacts 62 and 66 and closing the contacts 62 and 68. Likewise, the current of both motor windings is sufficient to hold contacts I4 and I6 closed regardless of motor speed. The movement of switch 60 results in reversing the connection to therunning winding I22 and in addition places the bimetal timer 84 This change in circuit may be traced by noting that when the reversing switch 60 is down, the circuit to the starting winding I22 from the bimetal actuator 64 is through the conductors I04, I06, coil 10 and conductors H2, H4 and H5 to the bottom contact 66 on the far side of the switch 58. However, when the switch 60 is in the up position, the circuit from the bimetal actuator 64 to the starting winding is through the conductors I04 and I06, relay coil I0, conductors H2 and H4 to the fixed end of the bimetal timer 04 and'thence through the conductor I I6 to the top contact 68 on the near side of the switch '60. Thus, the bimetal timer 84 is-placed in series with the starting windings-only when the switch 60 is in the top position in which the motor is connected for starting forwardly. The current to the starting windings passing through the bimetal timer 84 causes the same to warp, closing the contacts 86 and 88 after an interval long enough to permit the motor to come up to speed. The closing of the contacts 86 and 88 shunts the electro-magnet I0 by the circuit including conductors I I2 and H4, contacts 86 and 88, bimetal timer 84 and insufficient to actuate the same. It will be noted also that the bimetal actuator 64 carries the current for the running winding during normal running of the motor. The proportions of the bimetal actuator are, however, such that the normal running current is insufficient to hold the switch 60 in the up position and thus it is insured that at the beginning of an idle period, the reversing switch 60 will be in a position to connect the starting windings for reverse rotation.

It will thus be seen that the present invention provides a novel means and method for insuring the starting of a motor-compressor unit by giving it a reverse rotation before attempting to start it forwardly. Also, the mechanism for thus unloading the compressor is particularly adapted for use with hermetically sealed motor-compressor units and has the advantage that should the unloading mechanism become disarranged for any reason, it may be repaired or replaced without having to open the hermetically sealed casing of the motor-compressor unit.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In an intermittent motor-compressor unit, the combination of a compressor of the type in which the direction of fluid flow therethrough is reversed upon reverse rotation thereof, a reversible electric motor driving the compressor and having starting and running windings, and automatic means operable to connect both the starting and running windings to a source of current for reverse rotation after each period of idleness and subsequently to change said connections to produce forward rotation during the remainder of each operating period.

2. In an intermittent motor-compressor unit, the combination of a compressor of the type in which the direction of fluid flow therethrough is reversed upon reverse rotation thereof, a reversible electric motor driving the compressor and having starting and running windings, and automatic means operable to connect both the starting and running windings to a source of current for reverse rotation after each period of idleness, and subsequently to change the connections of one of said windings to the line while the other winding remains connected as before to produce forward rotation during operating period.

3. In an intermittent motor-compressor unit, the combination of a compressor of the type in which the direction of fluid flow therethrough is reversed upon reverse rotation thereof, a reversible electric motor driving the compressor and having starting, and running windings, and automatic means operable to connect both the starting and running windings to a source of current 'for reverse rotation after each period of idleness,

conductors I04 and I06. The armature I2 is,

therefore, permitted to rise and open the master contacts I4 and I6, thus interrupting the circuit The bimetal timer 84 is permitted to return nearly to normal position by the fact that the current to the running winding which continues to pass therethrough isinsufiicient to maintain it fully warped. Further en'ergizationof the armature 12 is prevented since the normal current 'to the running winding is and subsequently to change the connections of one of said windings to the line while the other winding remains connected as before to produce forward rotation, and thereafter to disconnect the starting winding.

4. In an intermittent motor-compressor unit, the combination of a compressor of the type in which the direction of fluid flow therethrough is reversed upon reverse rotation thereof, a reversible electric motor driving the compressor and having starting and running windings, and automatic means operable to connect both the the remainder of each starting and running windings to a source of current for reverse rotation after each period of idleness, and subsequently to change the con nections of one of said windings to the line while the other winding remains connected as before to produce forward rotation, and means conditioned for operation only after the windings are connected for forward rotation for disconnecting the starting winding.

5. In an intermittent motor-compressor unit, the combination of a compressor of the type in which thedirection of fluid flow therethrough is reversed upon reverse rotation thereof, a single phase induction motor having starting and running windings, a hermetically sealed casing surrounding the motor and compressor, and an automatic switch outside the casing automatically operable to connect both the starting and running windings to source of current for reverse rotation after each period of idleness and subsequently to change said connections to produce forward rotation during the remainder of each operating period.

6. An intermittently operated motor-compressor unit including a motor and a compressor driven by the motor, said compressor having a compressing chamber provided with a check valve 'at its outlet for preventing the flow of compressed gas back into the compressing chamber and a piston for the compressor capable of forcing gas from the compressing chamber through the check valve at its outlet when the motor operates in its forward direction, said piston being capable of sweeping gas from the compressor chamber through the inlet to the compression chamber when the motor operates in the reverse direction, said motor having starting and running windings and current responsive control means for first requiring the current to flow through one of said windings in a reverse direction to cause the motor to first turn in a reverse direction after a period of idleness and thereafter causing the current to flow through the motor windingsin a normal manner to cause the motor to start and run in the normal forward direction during the remainder of each operating period.

'7. A motor-pump unit comprising pumping means having a rotatable drive member and containing-a pumping chamber provided with means for preventing entrance of fluid'upon reverse rotation of the rotatable drive member to expel fluid from and to evacuate said pumping chamber upon the reverse rotation of the rotatable drive member for unloading said pumping chamber, a reversible electric motor for driving said pumping means through said rotatable drive member, automatic control means effective after a period of idleness of the unit for initially energizing said motor to operate in the reverse direction for reversely rotating said rotatable drive member of said pumping means to evacuate said pumping chamber for unloading said pumping means and then changing the energizing of said motor to operate said motor in the forward direction as-long as the motor remains energized irrespective of the length of time of energization of the motor, and a second control means'for controlling the energization and deenergization of the motor.

8. A motor-pump unit comprising a pumping means having a pumping chamber provided with means at the outlet of the pumping chamber for preventing the flow of fluid through the outlet into the pumping chamber, said pumping chamher being provided with a pumping member capable of being actuated in one direction to draw in fluid into the pumping chamber and expelling said fluid from the pumping chamber through said outlet, saidpumping member being capable of expelling fluid from the chamber through the inlet while preventing the entrance of additional fluid to evacuate the pumping chamber when actuated in the reverse direction, a reversible electric motor for actuating said pumping member, and current responsive control means for first requiring the electric motor to first actuate said pumping member in the reverse direction to unload the pumping means after every period of idleness and thereafter requiring the electric motor to actuate said pumping member in said one direction for pumping fluid during the remainder of every operating period.

9. A motor-pump unit comprising pumping means of the type which is unloaded upon reverse operation thereof, a reversible electric motor having starting and running circuits for operating said pumping means, a reversing switch means biased during idle periods to the reversing position for energizing said electric motor for reverse operation at the start of each operating period to operate the pumping means in the reverse direction to unload the pumping means, means for moving said reversing switch means from reversing to normal position for energizing the electric motor for starting in the normal forward direc-- tion, and additional switch means effective only when said reversing switch means is in the normal position for changing the energization of the electric motor starting circuit.

10. A motor-pump unit comprising pumping means of the type in which the pumping chamber is evacuated upon reverse actuation of the pumping means, reversible driving means for actuating said pumping means, and electric curent controlled means effective after every period of idleness of the motor-pump unitto require said reversible driving means to initially operate in the reverse direction to apply reverse actuation to the pumping means to evacuate the pumping chamber and unload the pumping means and thereafter to change the control of said reversible driving means to require the driving means to operate in the forward direction to normally actuate the pumping means for pumping purposes as long as the unit continues to operate irrespective of the length of time of operation.

11. A motor-pump unit comprising pumping means having a rotatable drive member and containing a pumping chamber provided with means for preventing the entrance of fluid upon reverse rotation of the rotatable drive member and provided with means for expelling fluid from and to evacuate said pumping chamber upon the reverse rotation of the rotatable drive member for unloading said pumping chamber, a reversible electric motor for driving said pumping means through said rotatable drive member, electric current controlled means effective after a period of idleness of the unit for initially energizing said motor to operate in the reverse direction for reversely rotating said rotatable drive member of said pumping means to evacuate said pumping chamber for unloading said pumping means and then changing the energization of said motor to operate said motor in the forward direction as long as the motor remains energized irrespective of the length of time of energization.

12. A motor-pump unit comprising pumping means having arotatable drive member and containing a pumping chamber provided with means for preventing the entrance of fluid upon reverse rotation of the rotatable drive member and provided with means for expelling fluid from and to evacuate said pumping chamber upon the reverse rotation of the rotatable drive member for unloading said pumping chamber, a reversible electric motor for driving said pumping means through said rotatable drive member, temperature controlled means efiective after a period of idleness of the unit for initially energizing said motor to operate in the reverse direction for reversely rotating said-rotatable drive member of said pumping means to evacuate said pumping chamber for unloading said pumping means and then changing the energization of said motor to operate said motor in the forward direction as long as the motor remains energized irrespective of the length of time of energization.

13. In an intermittent motor-compressor unit, the combination of a compressor of the type in which the direction ofv fluid flow therethrough is reversed upon reverse rotation thereof, a reversible electric motor driving the compressor, and automatic means operable to drive the motor in a reverse direction to unload the compressor after each period of idleness and subsequently to cause said motor to produce forward rotation during the remainder of each operating period.

GEORGE C. PEARCE. 

